Attachment for mercury-lamps.



C'. P, STEINMETZ. ATTACHMENT FOR MERCURY LAMPS. APPLICATION FILED 00122 1904.

Patented Nov. 16, 1909,

' Be it known that I, Guanine UNITED srarns PATENT OFFICE. CEJllIi-LE P. STEINI VIETZ, O13 SCIlENECTADY, 'llORK, ASSIGNOR 130 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW-YORK.

arracmunnr r03 MERCURY-LA PS.

Speciflcation of Letters Patent. Patented Nov. 16, 1909.

Application filed october' 22, 1904. Serial No. 229 525.

To whom it concern:

)mmz,a citizen of the United States, residing at Schenectady, in the county of Schenectady'and State of New York,. have invented certairfnew and useful Improve-v ments in Attachments for MercuryLamps, of which thefollowing is a specification.

This invention relates to means for in creasing the reliability and safety ot'vapor electric-lamps and similar translating de vices.

While-the invention is of general application, it is believed to be of particular value when'used in connection with lamps 0p stated in series on constant-current circuits.

It is well-known that'constant-current generators of the type ordinaril used in series lighting systems do not build up readily on open circuit, and as mercury vapor lamps have a very high starting resistance difficulty has heretofore been encountered in operating these lamps on series circuits.

My invention comprises means whereby the generating machine may start on a low resistance circuit and whereby the high resistance lamps are not inserted into the circuit' until the line current has attained a substantial value. My invention further embraces a self-re- ,ducing resistance device in shunt with each lamp so that if the lamp fails to start when thrown in circuit, or if for any reason fails to carry its normal current, the resistance device will increase in conductivity and carry the normal line current for an indefinite period.

Figure l is a diagrammatic representation of my invention as applied to a mercury lam and Fig. 2 is a detail view of the pre erred form of self-reducing resistance.

The mercury vapor lamp 1, which may be of ordinary form, comprises an upper electrode 2, a starting filament 3 of suitable resistance material, a mercury electrode 4, a magnetic plunger 5 floating in the mercury and incontact with the lower end of the filament- 3, and a solenoid 6 adapted tocontrol the movement of the plunger s 5. When the lamp is-thrown incircuit 'witli the constantcurrent generator 1, thesolenoid 6, which is,

connected in series witlrfilament 3 at starting, draws down the plunger 5 from its 190- P. S'rEIN- sition in contact with the lower end of filament 3, thus forming anincipient are which starts the lamp. As the'filament 3 has a.

. very high resistance, the total resistance of all the lampsin circuit is often so high that the dynamo-will notproperly build up to normal current. To overcome this diiiiculty I provide the automatic cut -in device 7 shown in Fig. 1, which consists of the magnetizing coil 7 in series with the lamp and a movable armature 8 actuated by coil 7. In shunt with the lamp and in series with the coil 7 is a conductor '9 through which the starting current of the dynamo may pass before themercury lamp is thrown in circuit. When the generating machine I is first started the armature 8 of the cut-in device is in a position to-complete the circuit through the conductor!) and as all the lamps 1 1 1*, etc. of the circuit are similarly short-circuited the generator will readily build up on the low-resistance circuit thus formed. When the line current has attained substantially it's normal value the current in coil 7 automatically lifts armature 8 and thus opens the circuit through conductor 9 and places the lamp directly in series with the line.

As previously stated, the initial resistanc of the mercury lamp is very high so that at starting the voltage drop across thelamp dynamos, and not only is the lighting s'erv-' ice interrupted but the insulation of the circuit is subjected to a severe strain. To overcome these difiiculties, I provide a self-reducing resistance 10 inshunt with the lamp.

'This resistance maybe of the form shown in Fig. 2 which comprises a metallic cylinder 11 threaded at each end and lined on the interior by a mica bushing 12. The selfreducing resistance material 13 consists'preferably of a granular mixture of magnetite and mica held in'place by two electrodes 14 ,may reach 150 to 200 volts, or even a higher p and 15 which fit snugly within the mica lining." Sleeves 16 and 17 are provided respectively for the electrodes 14 and 15 and are screw-threaded on the, outside of the pipe 11; Each sleeve is prov with hexagonalshoulders 18 and 1.8 a apted to form v a wrench seat. By screwing the two sleeves on the pipe 11 the electrodes 14 and 15 may be-moved toward each' other and so compress the resistance material 13. Annular washers 19 and 20 of mica or other suitable resistance material serve to insulate the electrodes l4 and 15 from their respective sleeves I mixture may contain magnetite and mica as in the built-up unit or may consist of magnetite alone or mixed with other elements. or compounds. These resistance units have a large negative temperature coetli- -reached its normal condition 0 cient and so have the peculiar propertyofi decreasing in resistance from a very value-to a very low value when traversed 52y the line current and heated thereby.

*ur does not occur instantaneously, but'onl after the lapse of several seconds whic property is of reat value when the resistance unit is use? for the purpose here shown.

The usual form of cut-outs used with incandescent and arc lamps, such as film cutouts, spark gaps, etc., is not adapted for use with mercury vapor lamps for the following reasons: The startin resistance of the mercury; lamp is very big I and when the lamp is used on 'a constant-current circuit vthe drop in voltage'across the lamp at starting may be as high as 200 volts and for an instant even very much higher, although'the running voltage of the lamp may be as low as 40 volts. This instantaneous high voltage will break down afilm' cut-out or spark up and thus permanently short-circuit the amp, even though the lamp isin perfect condition. The resistance unit herein described will stand the starting voltage of the lamp of 150 to 200 volts fonseveral seconds without decreasing greatly in-resistance and this interval is sufficiently long to allow the lamp to start even though the vacuum is not quite perfect. If at the expiration of this time the lam has not operation the resistance unit will rapidly decrease in resistance and finallycarry substantially all 1 the line current. T s time limit of the resistance unit I consider of great importanceas it allows the lamp ample opportunity to start and at the same tlme operates with certainty to short-circuit the lamp, if after 651 a slightly defective lampa'mple time to start,

a suitable interval the lam has notattained its normal running con it'ion. 3 Not only does this resistance unit have a time limit but it has a time limit which is a function of the current carried by the'resistance and hence of the-voltage-across the lamp. This allows thermore, this reduction in resistance for if the voltage across the resistance unit is only slightly above normal the resistance will hold up even a minute or two and thus permit the lamp to start, but if at the Qild of this interval the lamp is not normal 'l'flie resistance will cut it out entirely. On the other hand, if the lamp is broken or entirely opencircuited the excessive voltage at the terminals of the resistance unit will break it down in a very short interval of time. This feature of a variabletime limit is of value for the rotection of a great variety of translating evices when used ongconstantcurrent circuits. The resistance unil fhas the advantages of being free from movina parts,

and of carrying no appreciable curren when means for supplying current thereto, a vapor electric lamp, a conducting path insh'unt with said lamp, automatic means for decreasing the current in said shunt path when the line current reaches a predetermined value, and a self-reducing resistance shunt ing said lamp. v

2. The combination of an evacuated en: velop; electrodes within said envelop for maintaining a current flow therethrough, starting'means for initiating a current flow between said electrodes, said means having an appreciable time element, and a resistance permanently connected between said electrodes and having a negative temperature co-efficient.

3. The combination of a vapor electric ap-- paratus having a high initial resistance and a relatively low running resistance, and a resistance unit in shunt with said lamp, having a negative temperature co-efficient, and adapted normally to carry no appreciable current. v

4. In an electrical system, a series circuit,

a plurality of lamps supplied by said cire cult, said lamps having a high initial resistance and a relatively low running I'ESlSil-g ance and having an appreciable time inter val at starting, and a self-reducingresist;-

ance in shunt with each of said lamps Iand capable of withstanding a high potential during the normal starting intervalof'a' lamp, but adapted to break down if that interval is prolon ed.

with said lamp, said resistance having an appreciable time limit.

6. The combination of a mercury vapor lamp and a self-reducing resistance in shunt 5. The combination of a mercury vapor. lamp and a self-reducing resistance in shunt with said lamp, said resistance ba tling a variable time limit.

7. The combination of a mercury vapor lamp and a self-reducing resistance in shunt vith said 1 negative temperature sofiicient and a variable time limit.

8. In an eiec't'rical system, the combination of :1 series circuit, a plurality of transiating devices. in said circuit, and a self-reciucing resistance in shunt with each of said translating devices. said self-reducing resistances id resistance having a having a negaiive temperature cwefiicient and a. mriable time limit.

In Witness whereofii have hereunto set my hand this 19th (Flay m? Get-obey, 1904.

CHARLES STEENMETZ.

Witnesses:

BEIMAMIN HULL,

HELEN Om oxim 

